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Old August 29th 04, 02:47 AM
mike beauchamp
 
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Default antenna formula needed

Can anyone tell me what the proper formula for finding a odd multiple of a
wave legnth in inches would be?IM trying to build a four element vhf
vertical array.
does anyone out there have a link to some dos software or java that would
let me imput the frequency id like to find the odd quarter wavelength for,
and it would give me a list of the diffrent multiples of the wavelegnth. or
just a simple list of antenna formulas for finding the legnth in inches..
thanks


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Old August 30th 04, 08:28 AM
Richard Harrison
 
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Mike Beauchamp wrote:
"Can anyone tell me what the proper formula for finding a odd multiple
in inches would be?"

Wavelength in meters is 300 divided by frequency in MHz. A meter is
39.37 inches. Reduce the antenna length by about 5% for "end effect". A
balanced antenna is often 1/2-wavelength. An unbalanced antenna is often
1/4-wavelength. Antennas are usually nnear self-resonant lengths to
avoid reactive opposition to antenna current.

Search on VHF antenna lengths. For an odd frequency multiple, divide the
fundamental frequency length by the order of the multiple. For 3X the
frequency, the length will be approximately 1/3 the fundamental length.

Always cut the calculated lengths a little long. It`s easier to trim to
length than to augment a too short antenna in most cases.

Best regards, Richard Harrison, KB5WZI

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